A nuclease-stabilized synthetic ribozyme (ribonucleic acid enzyme) with potential anti-angiogenesis activity. Ribozyme RPI.4610 specifically recognizes the mRNA for FLT1 (vascular endothelial growth factor receptor 1; VEGFR1), and hydrolyzes the mRNA, thereby preventing VEGFR1 proteins from being made. This may prevent VEGF-stimulated angiogenesis in cancerous tissue and metastasis.